Recently, as a catalyst which can homopolymerize ethylene or copolymerize ethylene and .alpha.-olefin with a high polymerization activity, there is proposed a new catalyst for the polymerization of olefins comprising a transition metal compound such as metallocene compound of zirconium and an organic aluminum oxy compound. As a process for the homo- or copolymerization of ethylene by using such catalyst, there has been proposed, for example, in Japanese Patent Application Laid-open Nos. Sho 58(1983)-19309, Sho 60(1985)-35007, etc.
In such a prior art, it has been disclosed that as a transition metal compound component, a metallocene compound is available, which has an alkadienyl radical such as a cyclopentadienyl radical, etc, as a ligand for the transition metal, and further an alkyl radical, a halogen atom, etc.
However, the metallocene compound in such prior arts may show a high polymerization activity as a compound having a halogen atom bound directly to the transition metal atom, but need a treatment with alcohol or water after the polymerization depending on the kind of olefins and the process for the polymerization, so that hydrogen halide may be formed disadvantageously which may occur rusts and corrosions in equipments. Further, a metallocene compound having an alkyl radical bound directly to the metal atom has high polymerization activity relatively and does not form. undesirable hydrogen halide, but there are some disadvantages that it is extremely unstable to a little air or moisture, is apt to lower the catalyst activity remarkably by deterioration in the operation or to deteriorate with time in storage, as a result, a special care and equipment to the handling and storage of catalyst component are required. Thus, for example, as seen in Japanese Patent Application Laid-open No. Sho 62(1987)-230802, there has been proposed a process in which the halogen atom or alkyl radical bound to the metal atom is converted to an alkoxy or phenoxy radical to eliminate the formation of hydrogen halide and improve the stability of the metallocene compound. In this case, however, disadvantageously the activity as catalyst for the polymerization of olefins is in general lowered.
Accordingly, it has been strongly desired to develop as a metallocene compound, a transition metal compound, which satisfies at the same time three requirements that it does not contain a halogen atom directly bound to the metal atom, as a result, it does not generate undesirable hydrogen halide, that it is stable to air and moisture so that it may be dealt with easily and has a high storage stability and that it has a high activity on using as a catalyst for the polymerization of olefins. And also it has been strongly desired to provide a process for the polymerization of olefins therewith.
After studying earnestly in view of the present status as mentioned above,: it has been found that a metallocene compound may eliminate the disadvantages as mentioned above which has a radical comprising a cyclopentadienyl skeleton coordinated to the transition metal and in which an aromatic ring substituted with a special substituent is bound through an oxygen or a sulphur to the transition metal, and it shows an excellent activity on using it as a catalyst for the polymerization of olefins resulting in the accomplishment of the present invention.